Numerous studies have established that a substantial proportion of early adolescents are engaging in behaviors placing them at risk for HIV infection. Previous research regarding risk activities in youths has underscored the importance of identifying appropriate theoretical frameworks for constructing behavioral interventions designed to reduce risk behaviors. In the present study we hypothesize that one potential framework -the Health Belief Model - characterizes (and thereby predicts) youthful decision-making regarding sexual behavior and HIV infection. In this study a cohort of sexually inexperienced inner-city youths aged 9 to 12 years will be followed prospectively for three years. The study will be conducted among youths attending the Pediatric Ambulatory Center (PAC), University of Maryland, Baltimore. This population is ideally suited for the aims of this study because of the high rates of early initiation of sexual activity and an established tradition of discussing risk behaviors and affective characteristics with PAC professionals. The relationship of the HBM (as well as other psychologic and biologic variables) to the timing of onset of sexual activity, use of condoms, and numbers of sexual partners will be identified through systematic surveillance. The study will consist of a formative phase and a cohort phase. In the formative phase, using ethnographic techniques including focus group discussions, free-listing and pile-sorting, we shall identify culturally- meaningful domains which relate to each of the 5 dimensions of the HBM - awareness of the seriousness of the disease, personal vulnerability, efficacy of preventive measures, self-efficacy in executing these measures and a cue-to-action. A survey instrument will be developed which addresses each of these domains as well as other domains identified by the youths as important in the decision-making process. In the cohort phase, youths will be periodically surveyed with this instrument as well as for other salient biologic and psychologic characteristics. The relationship of the HBM and other models with sexual risk behaviors will be examined with multivariate analyses. This study will provide information as to the suitability of the HBM and other models to form the theoretic framework for the design of AIDS educational interventions in late preadolescents and early adolescents.